@Phaedrux It worked , I droped the current to 30% and increased the speed to 1000 and the feedback surprised me a lot. It's so kind of you to offer me so much valuable advice.

@Phaedrux It worked , I droped the current to 30% and increased the speed to 1000 and the feedback surprised me a lot. It's so kind of you to offer me so much valuable advice.

@Phaedrux I have tried to wire Z motors to different drivers(2 and 3), unfortunatly, the Z sensorless homing seems still failed. The following is my config.g file and homez.g file. If nothing is wrong, it is definitly the right time to take the endstop in consideration.

My config.g file

;Duet WiFi(固件版本3.3)的配置文件

; General preferences
G90                                ; Send absolute coordinates...
M83                                ; ...but relative extruder moves
M550 P"Y"                     ; Set machine name
M669 K0 X1:0:0:0:0 Y0:-1:0:0:0 Z0:0:1:0:0 U0:0:0:1:0 V0:0:0:0:1;Kinematics Profile for 5-axis (cartesian)

; network
M551 P"123456"                ; set password
M552 S1                              ; Enable network
M586 P0 S1                         ; Enable HTTP
M586 P1 S0                         ; Disable FTP
M586 P2 S0                         ; Disable Telnet
M587 S"A204_printer_04" P"junhua.zhao.04"  ;Set the Wi-Fi account and password

; Drive Mappings
M569 P0 S1                         ; Drive 0 goes forwards: X Axis
M569 P1 S1                         ; Drive 1 goes forwards: Y Axis
M569 P2 S1                         ; Drive 2 goes forwards: Z1 motor
M569 P3 S1                         ; Drive 3 goes forwards: Z2 motor
M569 P4 S1                         ; Drive 4 goes forwards: U Axis
M569 P5 S0                         ; Drive 5 goes backwards: V Axis
M584 X0 Y1 Z2:3 U4 V5                ; My Driver Mapping

;Microstepping 
M350 X16 Y16 Z16 U16 V16 I1        ; Configure microstepping with interpolation
M92 X100.00 Y100.00 Z400.00 U26.667 V35.556          ; Set steps per mm and steps per degree

;Speed
M566 X480.00 Y480.00 Z24.00 U480.00 V480.00 P1        ; Set maximum instantaneous speed changes (mm/min)
M203 X12000.00 Y12000.00 Z750.00 U5000.00 V12000.00     ;  Set maximum speeds (mm/min)
M201 X1000.00 Y1000.00 Z1000.00 U1000.00 V1000.00       ; Set accelerations (mm/s^2)
M906 X620.00 Y620.00 Z560.00 U1300.00 V1300.00 I10           ; Set motor currents (mA) and motor idle factor in percent
M84 S30                            ; Set idle timeout

; Axis Limit
M208 X-125:126   Y-92.3:50  Z125:-1 U-200:200 V-12000:12000                   ; Centre of the rotating bed is set to origin 0,0
M564 H0;                           ;allow unhomed movement


; Endstops for each Axis
M574 X1 S3                         ;Set endstops controlled by motor load detection
M574 Y1 S3                         ;Set endstops controlled by motor load detection
M574 Z2 S4                         ;configure sensorless endstop for high end on Z (Detected by two motors)

; Stallgaurd Sensitivy
M915 X S3 F0 H400 R1		       ; Set X axis Sensitivity
M915 Y S3 F0 H400 R1		       ; Set y axis Sensitivity
M915 Z S3 F0 H400 R1		       ; Set z axis Sensitivity


; Z-Probe (manual)
M558 P0 H15 F120 T6000             ; disable Z probe but set dive height, probe speed and travel speed


; Heatbed Heaters and Thermistor Bed
M140 H-1                           ; Disable heated bed

; Tool
M950 P0 C"Fan0" Q250				; creat tool P0 

My homez.g file

; homeZ.g
; 用于归零Z轴
;
; 由RepRapFirmware配置工具生成 版本V3.3.10 时间 Tue Nov 01 2022 15:02:12 GMT+0800 (中国标准时间)

M400                        ; Wait for current moves to finish
M913 Z50                    ; drop motor current to 50%
M400

G91                         ; relative positioning
;G1 H2 Y100 F10000           ; lift Y away
G1 H1 Z110 F700           ; move quickly to Z axis endstop and stop there (first pass)
G1 H2 Z-5 F700            ; go back a few mm
G1 H2 Z-115 F700           ; move Z axis to the mid

G90                         ; absolute positioning
M400
M913 Z100:100              ; return current to 100%
M400

@dc42 If I use a duex5 expension board, should I make some definition in config.g file to make sure both of the duet2 wifi and duex5 are enabled? I mean that changing the C parament of M950 command is needed and what else?

@Phaedrux Thanks buddy, I also have a duex5 panel and I also think endstop is a more convenient option. But if I choose endstop, I need to redesign the structure. So,I'll make a try first to wire the motors to different drivers and if plan A fails, the endstop will be the last way.

@Phaedrux
I have two Z motors, and both of them are connected to Drive2.
Does that mean the command M584 X0 Y1 Z2 U3 V4 is wrong？And what do I need to change?
For the Z axis driven by leadscrew, what's the best speed for it?12000 or just lower than 1000?
And I‘m grateful for your help.

@gloomyandy Thanks for your help, both of the Z motors are wired to Drive2 as shown below.

And does that mean that I also need to rewrite the Z50:50 into Z50?

@Phaedrux
config.g file

;Duet WiFi(固件版本3.3)的配置文件
; 用于启动时由固件执行
;
; 由RepRapFirmware配置工具生成 版本V3.3.10 时间 Tue Nov 01 2022 15:02:12 GMT+0800 (中国标准时间)

; General preferences
G90                                ; Send absolute coordinates...
M83                                ; ...but relative extruder moves
M550 P"Y"                          ; Set machine name
M669 K0 X1:0:0:0:0 Y0:-1:0:0:0 Z0:0:1:0:0 U0:0:0:1:0 V0:0:0:0:1;Kinematics Profile for 5-axis (cartesian)

; 网络
M551 P"123456"                     ; set password
M552 S1                            ; Enable network
M586 P0 S1                         ; Enable HTTP
M586 P1 S0                         ; Disable FTP
M586 P2 S0                         ; Disable Telnet
M587 S"A204_printer_04" P"junhua.zhao.04"  ;Set the Wi-Fi account and password

; Drive Mappings
M569 P0 S1                         ; Drive 0 goes backward: X Axis
M569 P1 S1                         ;Drive 1 goes backwards: Y Axis
M569 P2 S1                         ; Drive 2 goes backwards: Z Axis
M569 P3 S1                         ;Drive 3 goes forwards: U轴
M569 P4 S1                         ; Drive 4 goes forwards: V轴
M584 X0 Y1 Z2 U3 V4                ; My Driver Mapping

;Microstepping 
M350 X16 Y16 Z16 U16 V16 I1        ; Configure microstepping with interpolation
M92 X100.00 Y100.00 Z400.00 U26.667 V35.556          ; Set steps per mm and steps per degree

;Speed
M566 X480.00 Y480.00 Z24.00 E270.00 U480.00 V480.00 P1        ; Set maximum instantaneous speed changes (mm/min)
M203 X12000.00 Y12000.00 Z750.00 E1500.00 U5000.00 V12000.00     ; Set maximum speeds (mm/min)
M201 X1000.00 Y1000.00 Z1000.00 E1000.00 U1000.00 V1000.00       ; Set accelerations (mm/s^2)
M906 X620.00 Y620.00 Z560.00 E700.00 U1300.00 V1300.00 I10           ; Set motor currents (mA) and motor idle factor in percent
M84 S30                            ; Set idle timeout

; Axis Limit
M208 X-125:126   Y-92.3:50  Z125:-1 U-200:200 V-12000:12000                   ; Centre of the rotating bed is set to origin 0,0
M564 H0;                           ;allow unhomed movement


; Endstops for each Axis
M574 X1 S3                         ;Set endstops controlled by motor load detection
M574 Y1 S3                         ;Set endstops controlled by motor load detection
M574 Z2 S4                         ;configure sensorless endstop for high end on Z (Detected by two motors)

; Stallgaurd Sensitivy
M915 X S3 F0 H400 R1		       ; Set X axis Sensitivity
M915 Y S3 F0 H400 R1		       ; Set y axis Sensitivity
M915 Z S3 F0 H400 R1		       ;Set z axis Sensitivity


; Z-Probe (manual)
M558 P0 H15 F120 T6000             ; disable Z probe but set dive height, probe speed and travel speed


; Heatbed Heaters and Thermistor Bed
M140 H-1                           ;Disable heated bed

;Tool
M950 P0 C"Fan0" Q250				; creat tool P0 

homz.g file

; homeZ.g
;
; 由RepRapFirmware配置工具生成 版本V3.3.10 时间 Tue Nov 01 2022 15:02:12 GMT+0800 (中国标准时间)

M400                        ; Wait for current moves to finish
M913 Z50:50                ; drop motor current to 50%
M400

G91                         ; relative positioning
G1 H1 Z110 F12000           ; move quickly to Z axis endstop and stop there (first pass)
G1 H2 Z-5 F12000            ; go back a few mm
G1 H2 Z-115 F6000           ; move Z axis to the mid

G90                         ; absolute positioning
M400
M913 Z100:100              ; return current to 100%
M400

@dc42 It's really driven by a leadscrew. I'm developing a five-axis dispensing machine based on Prusa i3 just like FreddieHong did. And I have dropped the Z motor current to 35%,but luck didn't appear. Just like what you said the force provided by leadscrew makes it difficult to get sensorless homing.

@Phaedrux
Thanks buddy, it really worked well.
Now I'm facing another new problem that the pump-switching voltage does not match the panel-output-voltage. Because when I send G1 P0 S0 command, the control panel outputs 1.13V voltage and when I send P0 S1, it outputs 24V voltage. It's really difficult to adjust the voltage to 5V. Do you have any suggestions for that?
Finally, please allow me to express my thanks once again.

First of all, I have complicated the sensorless homing file of both X and Y axis. Fortunately, they all work. However, when I configure the Z axis homing file the same way that I configured the XY axis, it can't get the signal that the current of motors have changed when Z-axis arrived at the boundary.
I would appreciate your help very much.
The following is my config.g file and homez.g file;
By the way, my control board is duet2 wifi ,rrf 3.3

;config.g
;Axis Limit
M208 X-126:125 Y-92.3:50 Z125:-1 U-200:200 V-12000:12000 
                                                    ; Centre of the rotating bed is set to origin 0,0
M564 H0								; allow unhomed movement

; Endstops for each Axis
M574 X1 S3				                 ; Set endstops controlled by motor load detection
M574 Y1 S3                               ; Set endstops controlled by motor load detection
M574 Z2 S4                               ; configure sensorless endstop for high end on Z (Detected by two motors)

; Stallgaurd Sensitivy
M915 X S3 F0 H400 R1		                ; Set X axis Sensitivity
M915 Y S3 F0 H400 R1		                ; Set y axis Sensitivity
M915 Z S3 F0 H400 R1		                ; Set z axis Sensitivity


; homeZ.g
; 用于归零Z轴
;

M400                        ; Wait for current moves to finish
M913 X50 Y50:50                ; drop motor current to 50%
M400

G91                         ; relative positioning
G1 H2 Y100 F10000           ; move away Y axis
G1 H1 Z110 F12000           ; move quickly to Z axis endstop and stop there (first pass)
G1 H2 Z-5 F12000            ; go back 5 mm
G1 H2 Z-115 F6000           ; move Z axis to the mid

G90                         ; absolute positioning
M400
M913 X100 Y100:100              ; return current to 100%
M400